Résumé - Abstract
Dissolved organic matter (DOM) is often quantified as a part of wastewater and porewater analyses in mine waste studies; however, the compounds that make up this DOM and their individual contributions to biogeochemical behaviour are topics that warrant further investigation. This is particularly relevant in passive-treatment systems, where organic matter additions and biological activity may generate higher DOM concentrations. Tannins are a form of dissolved organic matter, consisting of plant-derived polyphenolic biopolymers. Owing to their abundant hydroxyl surface functional groups, tannins and engineered materials produced from tannins can interact with metal(loid) cations and have applications relevant to mining. Tannins affixed to biosorbents can be used to absorb and chelate heavy metal cations and recover precious metals from water, tannins or modified tannins are used in flotation as depressants for gangue minerals such as pyrite, pyrrhotite and calcite, and tannins can also be used in soil washing to chelate and solubilize toxic metal(loid)s in order to remove them from solids. Tannins can sorb to mineral surfaces such as quartz, clays, and Fe-hydroxides and alter the reactivity of the minerals, and they can also influence the microbiology and biogeochemical activity in ecosystems. This project will explore the role tannins play in metal mobility in the context of mine wastes and passive remediation systems. Batch experiments will be used to examine the interaction of tannins with minerals, metal(loid)s, and to investigate how tannins affect metal mobility. We will use techniques including near-edge absorption fine structure (NEXAFS) and micro X-ray fluorescence (microXRF) mapping to examine the interactions between metals, tannins, and mineral surfaces. This study will provide insights for optimizing mine waste remediation systems and help further our understanding of how organic materials affect passive remediation system performance.